The design of port layouts and terminals suitable for LNG carriers has to meet exceptionally high safety standards. The highly sensitive subject is always treated by responsible parties with the utmost concern for the design of inherently safe terminals. This is reached through the careful choice of the terminal location within the port and the definition of strict nautical procedures for the entrance, transit, mooring and loading/unloading of the vessel.
In this article, an outline of the maritime issues to be addressed if LNG offloading is envisaged is given. The issues are grouped around four main themes:
• Port infrastructure design
• Nautical ship operations
• Overall port shipping safety
The above themes are interrelated. In greenfield sites, many issues are free to determine, hence laying great emphasis on the design of the total (port) operation. In existing ports, often the port infrastructure (layout), supporting services (tugs, VTS, aids to navigation), and the other port users are boundary conditions in the process of defining the ship operations and in the assessment of the overall risk. However, the primary importance of safe LNG operations often allows changes and adaptations to the existing (supporting) infrastructure, traffic flows and operational procedures in the port.
Marin is covering a good deal of the above-mentioned nautical safety aspects because of its high quality modelling for manoeuvring, safety and mooring purposes. One of its latest LNG projects in Ferrol (Spain) is amongst others, a good example of an integrated, safety-driven terminal development project; some details of this project are included at the end of this article. This article focuses on the inshore LNG offloading terminals and jetties and does not cover the exposed offshore offloading concepts.
Themes in introducing LNG offloading in ports
Port infrastructure design and nautical ship operations The objective of the port design is, first of all, to guarantee the safe approach into the port, the safe berthing at the jetty and calm mooring at the same jetty as much as possible. Secondly, the infrastructure and operational procedures in place should enable the safe arrival and departure from the jetty or abort any entrance manoeuvre dur ing an on-board or on-shore emergency.
Greenfield port development sites or dedicated harbour basins require a port layout evaluation in relation to wave calmness (safe mooring) and the required stopping and manoeuvring space – obviously all against the background of port development cost optimisation and an acceptable downtime.
Natural or existing ports do not focus on port layout design in the first place (apart from minor adjustments), but evaluate admission policies in relation to downtime of the port against direct risks associated with critical entrance manoeuvres and the moored ship motions (wave penetration). The issues addressed during these evaluations result in:
• A validated port (dimensions of approach, entrance and basin) and jetty lay-out
• A safe port entrance and berthing envelope (weather window)
• A safe and calm mooring position
• An optimised tug assistance (escorting) configuration
• An aids to navigation plan to facilitate the port entrance and departure manoeuvres
• A ship and port operations manual covering all relevant procedures and nautical information
• Additional measures to cope with the evaluated emergency (risk control options)
The above types of evaluations require the use of (fast-time) simulation tools regarding the moored ship motions and the ship manoeuvring capabilities (or real-time simulator). Marin’s Nautical Centre, MSCN, closely cooperates to this end with Delft Hydraulics to assure high quality environmental input on currents and wave penetration.
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